Synthesis And Control Of Indium Oxide And Indium Phosphide Nanoscale Building Blocks

The indium oxide (In₂O₃) and indium phoshide (InP), important functional semiconductors, are versatile smart materials that have key applications in biosensing solar cells, solid-state optoelectronic devices, flat panel display materials, and so on. The importance of the distinct shape, size and chemical functionality of In₂O-3 and InP make them promising candidates in determining optical, catalytic and magnetic properties. Therefore, there are many reports on the synthesis of In₂O₃ and InP nanostructures such as nanowires, nanobelts, nanocubes, etc. But it is challenging to developing simple and novel synthetic approaches for building different In₂O₃ and InP nanoscale building blocks. In the paper, several simple, novel and practical experiments including thermal oxidation method, hydrolysis of In(Ac)6 " complex solution, carbothermal reduction CVD method, etc, were designed to synthesis and control In2O₃ and InP nanoscale building blocks with different morphologies:(1) Synthesis and size-control of multilayer hexagram-shaped In₂O₃ nanostructuresA hexagram-shaped InOOH nanostructures were prepared by a controlled hydrolysis of transparent In(Ac)63- complex solution in the mixture solution of ethylene glycol (EG) and water with a volume ratio of VEG : Vwater = 4 : 1 at 180-220 ℃ for the first time. By calcinations, the hexagram-shaped InOOH were converted into In₂O₃ and the In₂O₃ remained hexagram morphology. XRD reveals that the as-grown In₂O₃ has the hexagonal phase structure. In the experiments, the size of the InOOH can be simply decreased by increasing the reaction temperature. So the sizes of hexagram-shaped In₂O₃ can be controlled by choosing appropriate InOOH precursors with different sizes. It has been revealed that the morphology and the phase structures of the product were found to depend strongly on the effects of solvent such as ethanol, ethylene glycol and glycerin.(2) Synthesis of In2O3 octahedrons and self-assembly In2O3-SiO2 nanochains into chrysanthemum-like nanostructuresoctahedrons and self-assembly chrysanthemum-like In2C>3-SiO2 nanochains have been successfully synthesized on (111) silicon substrate and Au-coated (111) silicon substrate, respectively, between 1^03 and graphite powder at 980°C for 1 h in flowing nitrogen atmosphere. The size and density of these octahedrons could be easily controlled by tuning the distance between the central heating zones and the silicon substrate. Especially, the octahedrons were obtained without any catalytic action while the self-assembly chrysanthemum-like In2O3-SiO2 nanochains were firstly obtained using Au as the catalyst. The XRD patterns indicated that these two products were cubic structure.(3) Direct vapor-phase synthesis of I112O3 nanocones in airThis paper describes a vapor-phase approach to the facial synthesis of 1^03 nanocones supported on the surface of Au-coated indium particles. A typical procedure simply involved the thermal oxidation of indium in air within the temperature range of 900-1000°C. Au catalyst is necessary for the formation of the ^03 nanocones. The lengths of these nanocones increase with the increase of the reaction time.(4) Self-assembly of In/SiO2 coaxial nanocables into circle shapeThe In/SiO2 coaxial nanocables with an average diameter of 1.3 urn which self-assembled into circle shape have been synthesized on (111) silicon substrate by carbothermal reduction method between ^03 and graphite powder at 1040°C for 1 h in flowing nitrogen atmosphere. The SEM and TEM images indicated that some nanocables are In-filling, however, others are without In filling. In the fringe of the silicon substrate, some In/SiO2 nanocables are vertical, and self-assembled into circle shape. EDS analyses reveal that these nanocables were consisted of In core and the SiC>2 sheath.(5) A complexant-assisted hydrothermal procedure for growing well-dispersedInP nanocrystalsWell-dispersed InP nanocrystals have been synthesized via a hydrothermal reaction of In-EDTA complex with red phosphorus and KBH4 in aqueous solution at 160-200°C for 26 h. The InP Nanocrystals were characterized by XRD, Raman spectroscopy, and TEM. The TEM study revealed that the morphology of InP nanocrystals are well-dispersed spherical shape, the average particle diameter is about 16 run. The size of InP nanocrystals can be controlled by changing the reaction temperature. The average InP nanocrystallites diameter is increased from 9.1 to 16.3 nm as the temperature is increased from 160 to 200°C. The reaction mechanism is discussed.(6) Direct growth of InPnanowires on indium grains surfaceWe report the synthesis of uniform, dispersed InP nanowires on indium grains surface using the direct reaction of indium grains with red phosphorus at 600-800°C for 1 h in flowing nitrogen atmosphere. These products were characterized by SEM, Raman spectroscopy, and TEM. The optimal reaction temperature is 800°C. Especially, the method can avoid complex organometalHc reactions and toxic gas, decreasing the reaction temperture to the lowest limitation. The successful synthesis of high yield InP nanowires may have potential applications for preparing III —V semiconductor nanocrystals because of the simplicity and practicability of this route.